The present invention relates generally to alarm systems.
FIG. 1 is an example of a conventional MP3 player. MP3 player includes an interface 106, nonvolatile solid state memory 102, a decoder 110, a digital-to-analog (D/A) converter 147, an audio output 116, a key pad 108, a display 112, a controller 104, RAM 144 and ROM 145.
Controller 104 controls the operation of the MP3 player in accordance with a set of programmed instructions. Programmed instructions for controller 104 are stored in nonvolatile memory or ROM 145, and RAM 144 is provided as the working memory for controller 104
Typically, MP3 data, which is a digital compressed format representing music data, is initially stored on a personal computer 50 and is subsequently transferred to the MP3 player via interface 106, under control of controller 104. The MP3 data is stored in nonvolatile solid state memory 102. Interface 50 can implemented by a standard parallel port, serial port, USB and the like. Nonvolatile solid state memory 102 may be implemented as flash memory. Generally, for a music quality recording, a nonvolatile solid state memory having 64 Mbytes can store about 1 hour of music. Flash memory provides the capability of retaining the stored digital data even when the MP3 player is powered down. Once the digital data has been transferred to the MP3 player, it no longer needs to be connected to personal computer 50, and the MP3 player can play back the MP3 data autonomously from personal computer 50.
Decoder 110 functions to decode and decompress the MP3 data file stored in nonvolatile solid state memory 102. Decoder 110 decompresses the MP3 music file in accordance controller 104 according to the MP3 format, and decodes the decompressed music file into a bit stream form. The bit stream is then converted into analog form by digital to analog converter 147 for connection to a speaker, earphone and the like. A decoding program for the MP3 decoder function is stored in the ROM 145 and loaded to RAM 144 by controller 104 as required.
The MP3 player comprises a keypad 108 for allowing user control and interaction with the MP3 player. Such control may include power on/power off, music selection and volume. The MP3 also comprises a display 112 for displaying characters or graphics, such as a battery indicator, a play mode indicator, a volume indicator, available memory size and the title of the music being played.